The invention relates to a wheelchair having a turnbuckle assembly that acts in compression to maintain an adjustable height and angle of the seat relative to the drive axle.
It is an advantage to provide for a mechanism for height and seat angle adjustment for wheelchairs that allows easy use but can be locked into a desired position, which will be sustained during even the most active use of the wheelchair. The present invention presents an elegant design solution, which is suitable in particular for the demands of high performance wheelchairs.
The healthcare industry has become increasingly aware of the need of wheelchairs users who are vigorous and athletic despite their confinement to wheelchairs. The aesthetic of high performance wheelchairs corresponds to that of high performance bicycles. The equipment is designed to be lightweight but strong and facile so that the user feels that it is an extension of his or her own body. The paradigm of more from less provides for structures and mechanisms that are deceptively simple and elegant solutions to the problems presented. The present invention provides such an elegant solution to height adjustment, giving a maximum range of adjustment which is easily manipulated but which will stand up to even the most rigorous use. Of course, the invention can also be used on wheelchairs, which are deigned for regular use criteria, such as institutional manual chairs, and even power chairs.
The present invention utilizes a telescoping xe2x80x9csingle handle in linexe2x80x9d turnbuckle assembly which has a small diameter right hand screw cylinder attached to the seat frame and that telescopes into a larger hollow left hand screw cylinder attached to a crossbar member of the frame of the wheelchair. A hand grasp has an internal bore along its longitudinal axis, which has threads at one end that mate with the larger diameter cylinder threads. The other end has a restricted opening, which includes smaller diameter threads that mate with the smaller diameter cylinder. The bore has an internal shoulder area, which acts in concert with a snap button having a detent member that projects radially outwardly from the smaller diameter cylinder to stop the cylinder from being unscrewed from the turnbuckle assembly. Further, a locking mechanism, such as a jam nut or a pop lock, which springs into a seat, such as a groove in one of the sets of threads, maintains the set relationship of the two cylinders. The rearward cylinder is pivotally joined to the seat frame member. For example, the cylinder may be welded to a transverse tube, which captures opposing pivot pins that pivotally secure the tube to spaced bracket members attached to the seat frame rod. Thus, the transverse tube will pivot in relation to the seat frame member to allow for the change in angle as the turnbuckle is extended or contracted by rotation of the handgrip. A similar pivot assembly is provided for the cross frame member.
The present invention provides infinite adjustment over its range, an extended range of motion for a relatively small radial change in the hand grip, locking mechanisms to provide for a secured setting and to prohibit over-extension of the telescoping members, and an economically efficient and structurally elegant tight method of achieving seat height adjustment.